Elevation of gamma-aminobutyric acid (GABA) and essential amino acids in vacuum impregnation mediated germinated rice traced by MALDI imaging

Unveiling targeted spatial metabolome of rice seed at the dough stage using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry imaging

Rice (Oryza sativa) seeds contain a variety of metabolites, which not only provide energy for their own growth and development, but also are an important source of nutrition for humans. It is crucial to study the distribution of metabolites in rice seeds, but the spatial metabolome of rice seeds is rarely investigated. In this study, Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) imaging was used to reveal the spatial distribution of free soluble sugars (glucose, fructose, sucrose, and maltose), amino acids (9 essential amino acids and 2 amino acids affecting rice eating quality: L-aspartic acid and L-glutamic acid), and 4 metabolites in the flavonoids synthesis pathway (cinnamic acid, naringenin chalcone, naringenin, and dihydrokaempferol) in rice seed at the dough stage. It was found that the 4 free soluble sugars present similar spatial distribution, mainly distributed in the seed cortex and embryo with high abundance. The majority of amino acids are also concentrated in the rice cortex and embryo, while the others are abundant in the whole seed. Besides cinnamic acid distributed in the seed cortex and embryo, the naringenin chalcone, naringenin, and dihydrokaempferol were also found in the endosperm and had lower content. Furthermore, a colocalization phylogenetic tree according to the spatial distribution imaging of each metabolite was constructed. This study revealed the distribution diversity of metabolites in different segmentations of rice seed at the dough stage, providing clues for the nutritional differences between brown rice and white rice, and serving as a reference for people to target a healthy diet.

Health-promoting germinated rice and value-added foods: a comprehensive and systematic review of germination effects on brown rice

Over the last 30 years, thousands of articles have appeared examining the effects of soaking and germinating brown rice (BR). Variable germination conditions and methods have been employed to measure different health-beneficial parameters in a diverse germplasm of BR. Research results may therefore appear inconsistent with occasional anomalies, and it may be difficult to reach consensus concerning expected trends. Herein, we amassed a comprehensive review on germinated brown rice (GBR), attempting to codify 133 peer-reviewed articles regarding the effects on 164 chemical parameters related to health and nutrition in BR and in value-added food products. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-2020) approach was used to direct the flow of the literature search. A pair-wise comparison t-test was performed to deliver an overall approach indicating when a given compound has been found to significantly increase or decrease through germination, which was grouped into GABA and polyamines, γ-Oryzanol and phytosterols, phenolic compounds, vitamins, proteins and amino acids, starchy carbohydrates, free sugars, lipids, minerals and phytic acid. This resource will stimulate interest in germinating rice and optimistically help increase both production and consumption of highly nutritious, health-beneficial rice with pigmented bran.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Nutrient Composition of Germinated Foxtail Millet Flour Treated with Mixed Salt Solution and Slightly Acidic Electrolyzed Water

Germination of millet can improve its consumption quality, optimize its nutritional composition, and promote the accumulation of functional components such as γ-aminobutyric acid (GABA). In the present study, foxtail millet was germinated with tap water, a mixed salt solution of 7.5 mmol/L NaCl and 15 mmol/L CaCl₂, and slightly acidic electrolyzed water (SAEW) with three available chlorine concentrations (ACCs; 10.92, 20.25, and 30.35 mg/L). The effects of the salt solution and SAEW on the germination of foxtail millet and the GABA, crude protein, and amino acid composition of the germinated millet flour were analyzed. The results showed that the salt solution and SAEW treatments promoted the growth of millet sprouts, contributed to the accumulation of GABA in germinated millet flour, and optimized the protein and amino acid composition. The GABA content of germinated foxtail millet flour treated with salt solution for 60 h (336.52 mg/100 g) was 29.5 times higher than that of ungerminated millet flour. In conclusion, the highest GABA content and amino acid scores of germinated millet flour obtained by germination treatment with salt solution at 25 °C and 86% humidity for 60 h were more acceptable for human nutritional requirements.

The yield, nutritional value, umami components and mineral contents of the first-flush and second-flush Pleurotus pulmonarius mushrooms grown on three forestry wastes

This study was carried out to evaluate the yields and quality of the first-flush and second-flush Pleurotus pulmonarius mushrooms grown on three forestry wastes (pine, poplar, and honeysuckle rattan). The biological efficiency (BE) of the substrates varied from 61.89% to 81.01%. The total protein content, gamma-aminobutyric acid (GABA) content and equivalent umami concentration (EUC) values of the mushrooms were greatly influenced by the flush number and the substrate, however, the total sugar content and ergosterol content of the mushrooms were not significantly affected. The first-flush mushrooms that were grown on the pine sawdust-based substrate had the highest protein content, and the first-flush mushrooms that were grown on the honeysuckle rattan sawdust-based substrate had the highest GABA content and EUC values. All the mushroom samples accumulated Cu but excluded Ca, Mn, Pb, Cr, and Cd, and the concentrations of Mg, Fe, and Mn are species and flush number dependent.

Optimization of germination and ultrasonic-assisted extraction for the enhancement of γ-aminobutyric acid in pumpkin seed

Germination and ultrasonic-assisted extraction (UAE) are economical and effective methods to enhance bioactive compounds in plant seeds. We optimized the germination parameters and UAE parameters by using response surface methodology to maximize the recovery of γ-aminobutyric acid (GABA) in pumpkin seeds. The optimal germination conditions were as follows: soaking the seeds at 28°C for 6 h with 0.2% CaCl₂, 3.8 mg/ml monosodium glutamate, and 4.0 mg/ml vitamin B₆, then germination at 30°C for 61.6 h. The optimal conditions for UAE were as follows: 1:75 (w/v) material-to-solvent ratio, 220 W ultrasonic power, and ultrasonic treatment at 50°C for 14.4 min, which afforded an extraction yield of 2679 ± 10 mg/100 g. Moreover, the GABA-enhanced extract showed the potential of hypolipidemic effect in type 2 diabetes rats. These results confirmed that a combination of germination and UAE increased the GABA yield from pumpkin seeds and provided a basis for GABA-enhanced production to improve lifestyle-associated diseases.

Unravel the Local Complexity of Biological Environments by MALDI Mass Spectrometry Imaging

Classic metabolomic methods have proven to be very useful to study functional biology and variation in the chemical composition of different tissues. However, they do not provide any information in terms of spatial localization within fine structures. Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) does and reaches at best a spatial resolution of 0.25 μm depending on the laser setup, making it a very powerful tool to analyze the local complexity of biological samples at the cellular level. Here, we intend to give an overview of the diversity of the molecules and localizations analyzed using this method as well as to update on the latest adaptations made to circumvent the complexity of samples. MALDI MSI has been widely used in medical sciences and is now developing in research areas as diverse as entomology, microbiology, plant biology, and plant–microbe interactions, the rhizobia symbiosis being the most exhaustively described so far. Those are the fields of interest on which we will focus to demonstrate MALDI MSI strengths in characterizing the spatial distributions of metabolites, lipids, and peptides in relation to biological questions.